We previously developed a fluorescence adaptive optics scanning laser ophthalmoscope (FAOSLO) that can simultaneously resolve the cone and RPE mosaics in the living eye. Using this device, we have discovered two unexpected changes in RPE cell images following long duration exposure to visible light. The first is an immediate reduction in lipofuscin autofluorescence (AF) that recovers in several hours. This RPE AF photobleaching can be observed with exposures 2 orders of magnitude below the ANSI maximum permissible exposure (MPE). At irradiances at or even slightly below the ANSI MPE, we observed a second phenomenon characterized by a disruption in the RPE cell mosaic, which we call RPE photodamage. The mechanisms underlying these two phenomena are unknown, as are their consequences for vision. The importance of understanding the impact of these effects on vision is underscored by the proliferation of new retinal imaging technologies that use lights levels capable of producing them. During the next funding period, Janet Sparrow and her group at Columbia University will characterize the molecular changes associated with AF photobleaching and recovery, as well as RPE photodamage. David Williams and his colleagues at the University of Rochester will use in vivo imaging to determine whether RPE photodamage is linked to the visual cycle or a direct effect on lipofuscin in RPE cells. They also will determine whether AF photobleaching and RPE photodamage compromise receptor function or visual sensitivity. Not only will our joint effort advance understanding of interactions between light and the photoreceptor/RPE complex, it will also guide the ANSI committee in modifying the existing light safety standard. PUBLIC HEALTH RELEVANCE: Investigators at the University of Rochester and Columbia University will collaborate to discover the cause of a previously unknown form of light damage to the retina. This research could lead to improvements in the safety of ophthalmic devices for imaging the back of the eye and retinal surgery.